In a mobile communication system employing an LTE (Long Term Evolution)-Advanced scheme for which the 3GPP is developing a standardization, performing “CA (Carrier Aggregation)” has been discussed.
When the CA is being performed, a mobile station UE is configured to transmit uplink signals using a plurality of “Component Carriers (CCs)” having different frequency bands to a radio base station eNB.
Therefore, in the LTE-Advanced mobile communication system, it is considered that coverage areas of cells #11, #12, and #13 using CC of a frequency band F1 and coverage areas of cells #21, #22, and #23 using CC of a frequency band F2 are configured to be geographically superimposed with each other with the same size as shown in FIG. 4.
However, when a 2 GHz band is used as the frequency band F1 and a 3.5 GHz band is used as the frequency band F2, since the propagation characteristics of CC of the 3.5 GHz band are lower than the propagation characteristics of CC of the 2 GHz band, there is a problem that it becomes difficult to make equal to each other, the size of a coverage area of a cell using the CC of the 2 GHz band and the size of a coverage area of the cell using the CC of the 3.5 GHz band.
Particularly, there is a problem that a larger propagation attenuation occurs in a high frequency band such as a 3.5 GHz band or a 4.9 GHz band as compared with a frequency band such as a 2 GHz band generally used in a cellular system, and when it is assumed that the reception sensitivity of a mobile station UE is constant, a deterioration of about 4 dB to 10 dB occurs in terms of link budget. Therefore, in case of using the high frequency band such as the 3.5 GHz band or the 4.9 GHz band, there is a problem of not being able to guarantee a coverage, and there is also a problem of not being able to guarantee mobility.
For example, when a mobile station UE moves during communication using a carrier of the 3.5 GHz band, there is a problem that the mobile station UE may easily enter an area not covered with the carrier of the 3.5 GHz band, a handover may fail, or a call may be interrupted.
In order to solve these problems, it is considered to increase the density of a cell using the high frequency band such as the 3.5 GHz band or the 4.9 GHz band by increasing the number of radio base stations eNB; however, this leads to a problem that there occurs an increase in a network configuration cost.